Electrical wiring device and contact supporting structure therefor



M. EHRLICH ELECTRICAL WIRING DEVICE AND CONTACT Dec. 6, 1966 SUPPORTING STRUCTURE THEREFOR 2 Sheets-Sheet 1 Filed Jan. 31, 1964 4 z 7 M. u 4 4 y H 3 Q M a. a w% L H 7 III I w If r l W 57 4T fl 7 D .i

mm m my c M m A M Dec. 6, 1966 M. EHRLICH 3,290,465

ELECTRICAL WIRING DEVICE AND CONTACT SUPPORTING STRUCTURE THEREFOR Filed Jan. 51, 1964 2 Sheets-Sheet 2 INVENTOR. MMm/A MNEVQZ my United States Patent 3,290,465 ELECTRICAL WIRING DEVICE AND CONTACT SUPPORTING STRUTURE THEREFOR Maximilian Ehrlich, Baldwin, N.Y., assignor to Levlton Manufacturing Co., Inc, Brooklyn, N.Y., a corporation of New York Filed Jan. 31, 1964, Ser. No. 341,691 3 Claims. (Cl. 200-68) The present invention relates to improvements in electric wiring devices such as switches. It relates, more particularly, to electrical switches for use in alternating current circuits.

Generally speaking, electrical switches of the AC. type have a hollow housing molded (from plastic insulating material which comprises a base and a cover secured to and extending over the base. The electrical components, such as the contacts and contact-carrying members, are mounted within the base and an operating lever is pivotally mounted in the housing, with one end thereof extending through an opening in the cover to the exterior of the housing. A cam member carried by the operating lever engages with a spring contact-carrying arm and upon pivotal movement of the lever, a contact on the spring arm is moved into or out of engagement with an opposing contact.

In such switches, it is desirable to hold the opposing contacts in alignment with each other and to prevent movement of the fixed contact during operation of the switch. This prevents excessive arcing and consequent deterioration of the contact surfaces.

Thus, an object of the present invention is to provide a switch structure in which the contacts and other electrical components are positioned and held in desired positions by assembly of the various parts.

Another object of the present invention is to provide a switch structure in which the efiects of variations in dimensions or tolerances encountered in forming the electrical components and in the molding of the plastic housing are minimized and reliability in the performance and operation of the switch is improved.

A still further object of the invention is to provide a switch in which manufacture of the parts and their assembly is simplified.

Other objects and advantages of the invention will become apparent and be better understood from the following description and the accompanying drawings, in which:

FIG. 1 is a side elevational view in vertical section taken along the line 11 of FIG. 2 of an electrical switch of the A.-C. type which embodies the invention;

FIG. 2 is a view in section taken along line 2-2 of FIG. 1 of the switch shown in FIG. 1 with certain parts being omitted for clarity;

FIG. 3 is an end view in vertical section taken along line 33 of FIG. 2 of the switch shown in FIG. 1;

FIG. 4 is a fragmentary side view of the switch shown in FIG. 1 in section taken along line 44 of FIG. 2;

FIG. 5 is a side elevation view of the switch shown in FIG. 1 in partial section showing the operating parts of the switch in a different position; and

FIG. 6 is an exploded view in perspective of the electrical or current-carrying elements of the switch shown in FIG. 1.

The switch embodying the invention which is illustrated and described herein is a three-way switch. However, it will be understood that the invention is not limited to this particular .form of switch. It will also be understood that the present invention has application to electrical wiring devices other than switches.

Referring to the drawings, there is a hollow, box-like housing which includes a base 10 having a bottom 11 with end walls 12, 12' and side walls 13, 13' extending upwardice ly therefrom. A cover 14 rests on the upper edges of the side and end walls and a metal supporting strap or yoke 15 extends over the cover. In assembled condition, the cover and the strap are secured to the base by means of rivets, 16, 16' or other suitable fastening means which extend through the end walls of the base.

An operating lever 17 is pivotally mounted in the housing with one end thereof extending through an opening in the cover. The operating lever has trunnions 20, 20 extending outwardly from opposite sides thereof intermediate its ends which are journalled in bearings formed by troughs or recesses 21, 21' in the upper edges of the side walls of the base and opposing troughs or recesses 22, 22' in the lower face of the cover.

Motion of the operating lever in opposite directions is limited by engagement of an enlarged segment on the lever with rubber bumpers 23 or 23' (depending upon the direction) mounted on the .bottom of the base. The rubber bumpers are press-fitted into sockets 24 and 24' defined by vertical walls which extend upwardly from the bottom of the base and are preferably cylindrical in shape so that they need not be oriented for assembly.

The operating lever is biased toward one or the other of its two extreme positions by an open-ended, compressed coil spring 25. The coil spring is interposed between the lever and the bottom of the base with one end engaging with a thrust ridge 26 formed on the lever and the other end engaging with a thrust ridge 27 formed on the bottom of the base. The thrust ridges are parallel to the axis of rotation of the operating lever and the spring is centered relative to the thrust ridges by means of a conical guide 28 carried at the end of the lever and a conical guide 29 extending upwardly from the bottom of the base which extend into opposite ends of the coil spring. This eliminates the need for capping the ends of the spring to secure straight line action of the spring.

The electric elements or components of the switch are shown best in FIG. 6. These elements include fixed contacts 3t 30' which are carried on supporting arms, 31, 31', respectively. These contacts face downwardly and are located inside the housing with the support arms extending inwardly from diagonally opposite corners. Opposing contacts 32, 32 are carried on movable contact-carrying arms 33, 33, respectively, of a springy or resilient sheet material such as brass. The movable spring arms extend inwardly from the other pair of diagonally opposite corners to a point just beyond the center of the housing with the contacts thereon facing upwardly in opposing relation to the first mentioned contacts. By locating the opposing contacts close to the center of the switch, as may best be seen in FIG. 2, the effect of long lever arms and dimensional variations in the parts is minimized. The contact arms are of cantilever design and in each instance, the contacts carried by the movable arms are positioned beneath the fixed contacts with the movable spring arms being biased to urge the contacts thereon into engagement with the opposing fixed contacts.

The trunnions of the operating lever have downwardly extending cam members 34, 34 formed thereon and each of the cam members is positioned to engage with one of the movable contact-carrying arms at a point adjacent the contact thereon. One of the cam members engages with and depresses one of the arms in movement of the lever in one direction, while the other cam member engages with and depresses the other arm in movement of the lever in the opposite direction. For example, in the position of the lever shown in FIG. 1, cam 34 is out of engagement with movable contact-carrying arm 33 and permits the contactcarrying arm to urge the contact 32 carried thereon into engagement with the opposing fixed contact 30 while cam member 34 engages with and depresses the other movable contact-carrying arm 33 causing the contact 32' carried thereon to be separated from its opposing contact 30. Movement of the operating lever to the position shown in FIG. reverses this condition.

The cam members engage with the movable contactcarrying arms at points close to the contacts carried thereon. By keeping the distance between the contact and the point at which the cam engages with the arm as small as possible, the effects of variations in the dimensions of the cams or the positioning of the cam carrying lever in the housing are minimized. In other words, errors or variations in the dimensions or positioning of the cam will not be multiplied by a long arm extending beyond the points at which the cam engages therewith.

It will also be noted that in the three-way switch illustrated, the movable contact-carrying arms are located on opposite sides of the operating lever and extend in opposite directions so that their action on the lever in movement thereof will be balanced. In other words, the symmetry of the switch is such that forces exerted on the operating lever are the same when it is thrown to one side of its dead center position as when it is thrown to the other side.

In each instance, the movable and fixed contact-carrying arms are preferably formed integrally with flat terminal or support plates 36, 36', 38 and 38 of sheet metal, such as brass. The movable contact-carrying arms 33 and 33 are connected by lateral extensions 35 and 35' to their respective terminal or support plates 36 and 36' and the fixed contact arms 31 and 31 are connected by lateral extensions 37 and 37' to their respective support plates 38 and 38'.

In assembled condition, the support plates extend vertically along the side walls 13 and 13' of the base at the corners thereof. As may best be seen in FIG. 2, a vertical edge of each support plate is received in a vertical slot formed in an upstanding wall of the base, while the other edge engages with an abutment formed by an opposing wall facing but spaced from said slot. In the case of supports plates 38, 38' for the fixed contacts, the slots are defined by bosses 39, 39' projecting inwardly from the end walls. In the case of support plates 36, 36' for the movable contacts, the slots are defined by bosses 4t), 40 which project inwardly from the side walls of the base and have turned-over flanges or lips 41, 41' which extend over the edges of the plates.

The slots in the molded base are dimensioned to make a sliding fit with the support plates so that the plates can be dropped therein in assembly of the parts. This prevents damage to or breakage of the molded parts such as is apt to happen when force fits are attempted and it avoids the necessity of holding the parts to close tolerances. However, the support plates, especially those for the fixed contacts, should be firmly held in place in the assembled switch to maintain the desired alignment of the contacts. Also, movement of the fixed contacts or the support plates therefore is apt to give rise to chatter or rebound of the fixed contacts with respect to the movable contacts under sudden closing of the contacts and a quick succession of make-and-break connections between opposing contacts resulting therefrom will give rise to excessive arcing and damage the contacts, thus reducing their life and effectivemess.

The desired positioning and holding of the terminal or support plates in place in the housing is accomplished by forming a resilient or compressible portion at one end of the plate in the form of a finger 42 which is separated from the remainder of the plate by a V-shaped slot extending partially across the plate to a point adjacent its other side. The plates extend vertically along the side walls of the housing base to a point above the top edges thereof. Thus, the plates and the resilient fingers are placed under compression when the cover is placed on top of the base and is secured thereto.

The resilient fingers 42 may be formed on the plates by shearing or slitting the plates transversely part way across their width. This forms a cut in the plate which extends parallel to the upper edges thereof and the plate is then peened at the inner end of the cut producing dimples 43 and causing the cut to open into the V-shaped slot, as shown in FIGS. 4 and 6. The upper edges of the support plates fit into vertically extending recessses 44 in the underside of the cover and the dimensions of these parts are such that when the cover is tightly secured in place, the resilient or compressible finger portions of the plate are under compression with the result that the support plates are firmly secured in fixed positions without special fastening means.

If desired, pierced and tapped holes 45 may be formed in the terminal or support plates to receive terminal screws 46 for fastening electric wires thereto. The terminal screws are inserted into tapped holes and their inner ends are peened over slightly before the support plates are inserted in the base. To accommodate the screws, slotted openings 47 are formed in the side walls of the base and extend from the top edges of the side walls to the bottom thereof.

In the switch illustrated, an electrical shunt member 48 formed of sheet metal extends across the bottom of the housing and connects the support or terminal plate 36 for one movable arm to the support or terminal plate 38 for one fixed arm. The shunt member extends beneath the bottom ends of these plates and good electrical contact between the plates and the shunt member is insured by downward pressure of the cover forcing the lower ends of the plates into engagement with the shunt member, as may est be seen in FIG. 3. In addition, upstanding ends 49 and '50 of the shunt member which are bowed at 51 and 52 to provide a spring action also engage with the movable contact arm 33 and the support plate 38.

Upwardly extending vertical posts 53 which are located on opposite sides of the trunnion receiving recesses in the side walls of the base enter mating recesses 54 in the lower surface of the cover and serve to align the cover with a base. They also position the operating lever during assembly prior to the cover being secured to the base.

It will be understood that various changes and modifications in the embodiment of the invention illustrated and described herein may be made by those skilled in the art without departing from the spirit or scope of the invention as defined by the following claims.

What is claimed is:

1. In an electrical switch of the quiet type for. use with alternating current, the combination which comprises a hollow housing of insulating material, said housing ineluding a base and a cover, said base having a bottom and side walls extending upwardly therefrom, said cover being supported on said walls and having an opening therein, an operating lever pivotally mounted between the cover and the base with an end thereof extending through the opening in the cover, said lever being manually movable between a first position and a second position thereof, a spring guide member carried by the lever, a centrally located spring guide member extending upwardly from the base in alignment with the spring guide member carried by the operating lever, an uncapped coil spring extending between the lever and the base and engaging at opposite ends thereof with the spring guide members on the lever and the base, said spring biasing the lever toward one of its positions upon movement of the lever past a central point in its movement toward its said position, a set of electrical contact elements located within the housing on each side of the operating lever, each set of contact elements being similar and including a movable spring contact carrying arm and a fixed contact carrying am, said movable contact carrying arms having straight portions extending inwardly across the housing in opposite directions to a point beyond the center thereof and being biased toward the fixed arm, contact buttons carried on the ends of the fixed and movable contact arms, the contact buttons on the movable and fixed arms being in opposing relation to each other, cam members carried by the operating lever 5 on opposite sides thereof, one of said cam members being positioned to engage and depress the movable arm of one set of the contact elements in movement of the operating lever toward one of its positions, the other of said cam members being positioned to engage and depress the movable arm of the other set of the contact elements in movement of the operating lever toward its other position whereby theopposing contact buttons of each set'of contact elements are alternately opened and closed in movement of the operating lever between its two positions and means for supporting the contact elements of each set in fixed positions within the housing, said means including a supporting plate of conductive material attached to on end of each of the contact carrying arms and extending lengthwise between the cover and the bottom of the housing, each of said plates having a transverse slot extending partially across the plate intermediate its ends, said slots defining portions of the plates which are urged toward each other under endwise engagement of the plates between opposing surfaces of the cover and the base of the housing.

2. In an electrical switch, the combination as defined in claim 1 wherein the upstanding side walls of the base contain at least one vertically extending opening and one of the contact-carrying plates is located on the interior of the housing behind said opening, said plate including a terminal portion accessible through said opening.

3. In an electrical wiring device having a hollow housing of insulating material which includes a base having a bottom and upstanding side walls defining an opening in the base and a cover resting on said side walls and extending over said opening, the improvement which comprises, an electrical contact located within said hollow housing and a terminal plate of conductive material connected to and supporting said contact, said plate extending lengthwise between the cover and the bottom of the base of the housing with opposite ends of the plate being engaged thereby under a compressive force and having a transverse slot extending across a substantial part of its width intermediate its ends, said slot separating the plate into portions which are capable of being forced towards each other under engagement of the cover and the bottom of the housing with the ends of the plate whereby the plate is rigidly held in a fixed position relative to the housing.

References Cited by the Examiner UNITED STATES PATENTS 2,725,438 11/1955 Bentley.

2,795,677 6/1957 Slater.

2,881,279 4/1959 Taylor 200168 2,906,835 9/ 1959 Schmidinger 200113.1 X 3,178,530 4/1965 Lawson 200-68 X ROBERT Ki SCI-IAEFER, Primary Examiner.

D. SMITH, JR., Assistant Examiner. 

3. IN AN ELECTRICAL WIRING DEVICE HAVING A HOLLOW HOUSING OF INSULATING MATERIAL WHICH INCLUDES A BASE HAVING A BOTTOM AND UPSTANDING SIDE WALLS DEFINING AN OPENING IN THE BASE AND A COVER RESTING ON SAID SIDE WALLS AND EXTENDING OVER SAID OPENING, THE IMPROVEMENT WHICH COMPRISES, AN ELECTRICAL CONTACT LOCATED WITHIN SAID HOLLOW HOUSING A TERMINAL PLATE OF CONDUCTIVE MATERIAL CONNECTED TO AND SUPPORTING SAID CONTACT, SAID PLATE EXTENDING LENGTHWISE BETWEEN THE COVER AND THE BOTTOM OF THE BASE OF THE HOUSING WITH OPPOSITE ENDS OF THE PLATE BEING 